The field to which this invention pertains is heat curable coating compositions made from aqueous dispersions of epoxy resins or polyether resins derived therefrom and aminoplast or phenolplast resins.
Aqueous dispersions of polyepoxide resins and processes for making such dispersions are described in U.S. Pat. No. 2,872,427. Such dispersions can contain, in addition to polyepoxide resins, urea-formaldehyde resins and phenol-formaldehyde resins. Curing agents include various acid-acting and alkaline-acting materials.
A process for preparing aqueous dispersions of polyepoxide resins is described in U.S. Pat. No. 3,879,324. However, no curing systems are set forth in this reference.
Heat curable coating compositions made from aqueous dispersions are described in U.S. Pat. No. 3,908,049. These dispersions are made from a major amount of a carboxylic acid containing copolymer and a minor amount of a polyepoxide resin or an aminoplast resin.
U.S. Pat. No. 2,794,754 teaches the preparation of alcohol/water solutions of polyepoxide compounds and methylol compounds using acids, e.g., phosphoric acid, as catalysts. Curable coating compositions made from organic solutions of polyepoxide resins, phenol-formaldehyde resins and phosphoric acid are described in U.S. Pat. No. 2,699,413.
Adducts of polyepoxide resins and phosphoric acid are set forth in U.S. Pat. No. 2,541,027. These adducts are used as curing agents for polyepoxide resins.